The invention generally relates to bioremediation and more particularly relates to extraction and processing of ground water from a contaminated area in a pressurized bioreactor and reinjection of the treated water back into the contaminated area along with oxygen, nutrients, and finely dispersed native microorganisms.
A number of systems and processes have been developed for remediating subsurface soil and ground water that have been contaminated with hydrocarbons or other organic compounds. Early efforts involved prohibitively expensive excavation of contaminated soil. In situ processes include removal of contaminated ground water by pumping, cleaning the water by above ground treatment, and reintroducing the water into the ground water.
Bioremediation involves the use of biological media to decompose organic compounds. This can occur in situ or above ground and can use naturally occurring or specially cultured biological media. Above ground vessels in which biological treatment of ground water is undertaken are called bioreactors. The use in remediation of microorganisms that are naturally occurring or native to the area of the contamination is believed to be advantageous, because the native microorganisms are already adapted to the soil conditions and the contaminants. The challenge is to stimulate the proliferation of these naturally occurring microorganisms and provide a compatible environment for biological action on the contaminants. Without assistance, natural biological breakdown of contaminants in the soil can take an undesirably long time.
Bioreactors typically require multiple pumps, one to supply groundwater to the bioreactor and another to return the groundwater to the contamination zone. Bioreactors also tend to clog up with biomass as the biomass grows in the bioreactor. Electrically operated mixing devices are typically employed to break up the biomass colonies as they enlarge. Bioreactors employing multiple pumps and electrically operated mixers are expensive, require maintenance, and have not been entirely satisfactory.
An object of the present invention is to provide an improved process and bioreactor apparatus for enhancing the rate and efficiency of bioremediation in contaminated soil and ground water using naturally occurring biological media.